The present invention relates to a manufacturing method and manufacturing apparatus for making a optical recording medium such as a video disk, a compact disk, or the like, and more particularly to a method of manufacturing an optical recording surface and an apparatus for manufacturing a multi-layer optical recording medium.
FIG. 1 is a schematic view showing a structure of a conventional optical recording medium.
The optical recording medium is made of general transparent resin material, and has the structure of a transparent substrate 10 having a recording surface 11 in which a pit pattern is formed on an upper surface of the transparent substrate 10. A reflection film 12 of metal is evaporatedly formed by an evaporation process, such as sputtering process or the like, on recording surface 11. A protection film 14 or a substrate is formed on the reflection film 12. The pit pattern of the transparent substrate 10 and the reflection film 12 are formed to have the same shape or contour.
An optical disk as described above is read i.e., optical information obtained, by a process in which light from optical means is irradiated to the reflecting film and reflected in a predictable manner.
However, this conventional optical disk structure has a drawback: the storage capacity of the optical disk is insufficient for storage of a large amount of information, for example, when voice information as well as picture information are required.
Accordingly, a multi-layer recording medium structure is proposed as one method of creating a large storage capacity for information.
The Philips Co. proposed a multi-layer optical recording medium structure having a reflecting layer including reflecting coefficients which are different from one another (U.S. Pat. No. 4,450,553). The Pioneer Co. proposed a multi-layer optical recording medium structure composed of silicon as a first reflecting layer and aluminum second reflecting layer. (U.S. Pat. No. 5,126,996.
FIG. 2 is a schematic view showing the multi-layer optical recording medium structure proposed by the Philips Co.
The mulyi-layer optical recording medium is composed of a transparent substrate 20 made of a thick PVC plate of about 1 mm, a first resin layer 22 formed on the first transparent substrate 20 and processed by ultraviolet rays, a first reflecting film 24 formed on the first resin layer 22, a first adhesion layer formed on first reflecting film 24, spacing sheet 28 located on the first adhesion layer 26 and formed by a thick PVC plate of about 0.15 mm, a second adhesion layer 31 formed on the spacing sheet 28, a second reflecting film 32 formed on a second adhesion layer 31, second resin layer 34 formed on the second reflecting film 32 and processed by ultraviolet rays, and a second transparent substrate 36. The first reflecting film 24 adheres to the spacing sheet 28 by the first adhesion layer 26, and second a reflecting film 32 adheres to spacing sheet 28 by the second adhesion layer 31.
The conventional optical recording medium composed as described above has an optical structure of at least two layers. In each of the optical structures, the reflecting layers have different reflecting coefficients compared to one another. The stronger an intensity of the light reflected from the reflecting layers, the more precisely read the information. The ratio of incident light to reflected light depends on the reflecting optical structure. Of the two layers of the reflecting optical structure as shown in FIG. 2, the first reflecting film 24 is formed of, for example, dielectric material so as to pass through part of a radiation beam (.lambda.) from a light source. In such structure, the reflecting percentage of a level is needed in order to read out precisely the information in the first and second reflecting film 24,32, and it is preferable that the reflecting percentage of first reflecting film is 25-40%, and the reflecting percentage of second reflecting film 32 is 45-100%.
As shown in FIG. 3, the method of manufacturing the multi-layer optical recording medium as described above is proposed to comprise the steps of: forming a first reflecting layer 41 using silicon on a transparent substrate 40; injecting resin in a gel state in order to form a resin layer 42 on the reflecting layer 41; irradiating light in order to cure the resin after being stamped by an adhering stamp 44; and forming another reflecting layer 45 on an upper portion of a transparent resin layer 42.
After the resin is interposed between the adhering stamp 44 and transparent substrate 40, since resin is spread by pressing the adhering stamp 44 and transparent substrate 40, there is a problem that thickness distribution of the spread resin layer 42 is great. Also, since the above method executes comparatively many process steps and many man hours are necessitated by the many steps, and it was impossible to further improve productivity.